Observations of Ice-Ocean Eddy Streets in the Sea of Okhotsk off the Hokkaido Coast Using Radar Images

Abstract

This study examines the features of fairly regular ocean-wave motion in which some eddy streets or backward breaking waves are successfully visualized using sea ice floes as a tracer. These examinations are made using the time sequence of radar imagery data collected during the past 20 years, 1969–88; the correspondence of the radar images with the actual pattern is partially confirmed through aircraft observations. The ice-ocean eddy street or backward breaking wave pattern runs parallel to the coastline at a distance of about 20 km from the Hokkaido coast; the eddy street also corresponds to a boundary between the Soya Warm Current and colder, less saline offshore water. The wave motion is characterized by wavelengths of 40–55 km, phase velocities of 14–20 km day −1 and periods of 2.3–3.5 days. The regular ice-ocean wave motion pattern was observed when pack ice had a small ice concentration composed of uniform sized ice floes and weak winds. The sea ice floes serve as a highly effective flow indicator in the radar observations of the ice-ocean wave motion.